The issue in Crawford v. Marion County Election Board is likely to boil down to a complex legal concept that lawyers call the "level of scrutiny." This refers to the degree of proof that courts require to justify a government action. If a law restricts a trivial right, such as the right to smoke in public, all they need is a decent reason; if it restricts a fundamental right, like the right to travel interstate, officials must offer a convincing explanation and actual facts to support the law.

So the question will be: is making it burdensome or impossible for some people to vote a trivial abridgment or a serious impairment of an important part of full citizenship? Posner's opinion makes clear his view that casting an individual vote is no big deal. He cites a 1992 Supreme Court case, Burdick v. Takushi, that upheld a Hawaii ban on write-in voting. In Burdick, the Court said that strict scrutiny applied only to "severe" burdens of the individual's right to participate in elections. Regulations that, for example, limit the choice of candidates, however, need only be "reasonable" and "nondiscriminatory." (Interestingly, Justice Anthony Kennedy, whose vote is always decisive in close cases, dissented in Burdick, holding that the Hawaii write-in ban did not pass even loose scrutiny.)

But Burdick concerned the voters' right to choose a candidate not on the ballot--the Hawaii law did not deprive anyone of the right to cast a vote. Earlier cases have suggested that measures barring voters altogether are subject to "strict scrutiny," the standard that applies to proving government discrimination by race. If strict scrutiny is in effect, then officials in Indiana and elsewhere would actually have to produce facts to support their statute. It would certainly be impossible to be as flippant as Posner was about the flaws in the Indiana statute: "Perhaps the Indiana law can be improved--what can't be?"

The subtext of this case, and of the war over the vote, is a defect in America's patchwork Constitution. Unlike virtually every modern democratic constitution, ours nowhere explicitly guarantees every competent citizen the right to vote. States can't restrict the vote by race, or sex, or failure to pay a poll tax, or by age for anyone over 18; but the document nowhere says that eligible voters have a right to their vote. In fact, when Supreme Court Justices discuss voting rights, they often refer to this most basic of rights in scare quotes--"the 'right' to vote." This allows judges to adopt a kind of faux neutrality: some people want to vote; others don't want them to vote--the outcome is merely a matter of expediency.

This is desperately wrongheaded. In virtually every other advanced democracy, voting has a positive value: it is not up to the citizen to seek out a registrar or produce a satisfactory ID. Instead, the government itself is required to find and register every eligible voter and, if necessary, to provide each voter with an official ID without charge.

Amending the Constitution to guarantee the vote is an important long-term goal. But Congress can do much to ensure that this mischief does not grow, spread and become entrenched. Article I, Section 4, declares that the states shall regulate elections, unless Congress steps in. Congress could pass a statute requiring states to conduct fair, nonpartisan registration and to allow citizens to vote with a signature.

Currently before Congress are a variety of piecemeal reforms. Hillary Clinton's wide-ranging Count Every Vote bill would require states to accept an affidavit of citizenship as part of the mail-in registration process and would make it harder for state officials to toss out mail-in registrations for small errors. Barack Obama has a narrower bill aimed at measures that deceive voters about their eligibility. Representative Keith Ellison has offered legislation to block state ID requirements, but his bill has sparked little support.

The ID issue should be higher on the Democratic agenda. Voting is more than a matter of individual preference, like Coke or Pepsi. Free participation protects our political system from a more insidious kind of corruption in which elites govern without undue worry about public repudiation.

Vote suppression in the United States has a long and sordid past and present. Anonymous postcards often warn registered voters in black neighborhoods that they are ineligible. Fliers warn that any voter with an outstanding warrant will be arrested at the polls. Phone calls threaten eligible voters with criminal prosecution.

Thirty years ago, I saw white Southern registrars driving black voters away by threatening them with federal voter fraud charges. In 2004 I received an e-mail from my son, from a Southern election headquarters. He was fielding calls from black voters who were being turned away from the polls for minor errors in registration or failure to show an ID.

It is mortifying that we are passing this mortal flaw in our system down to the next generation. Voting lies at the heart of our national life, and efforts to restrict it to the "right" people corrode our very commitment to freedom. Perhaps we should consider radical change in our system.